some questions

[reimers84]

um i figured this was the best forum but I'm not sure if these questions are not meant to be posted in this form I'm sorry. these are just a few questions that have been bugging me, figured if i could get a few people to debate them that i might have a better understanding of their possible answers.

- we blueprint an action true the lugs and the bolt face etc etc to get the cartridge to align better with the bore, we also routinely debate which shoulders and tapers of a cartridge give the most concentric fit belted non belted etc etc. some even have their chambers custom machined to specific tolerances under the idea that a factory chamber allows not enough or to much expansion of their brass or to much play, concerned that the projectile will enter the bore slightly off axis. my question: does the plunger style ejector used on many actions exert force on the cartridge while being chambered and while in the bore, if it does wouldn't this be slightly side loading the cartridge against one of the sides of the chamber? wouldn't a standing ejector allow for a better fit between the round and the bolt face we took the time to true?
-Some makers have machined multiple smaller lugs from a full-lug-diameter bolt body, and this possibly encourages smoother bolt travel by virtue of the larger bolt body. is this true? is the strength of the action degraded? are their methods that can be implemented to smooth bolt travel on a regular lug design.
- u can reduce bolt handle lift by using three or more lugs which may speed up cycle time but it reduces the leverage u have on the bolt right? if the bolt handle was lengthened to compensate for the mechanical disadvantage would u really be gaining anything in the travel of the bolt handle, is their a sweet spot between bolt handle travel in degrees and length of handle for leverage? wouldn't 4 lugs machined to seat flush like blueprinted 2 lug actions have an advantage being they would better cover more axis of movement under recoil? what are the advantages of the 2 lug bolts over other designs.
-wont even a fairly small spread in velocity of one's ammo void the work he has done in barrel harmonics on a rifle, i mean if you want the round to exit just before the climax in the upward swing of a barrel then u are basically trying to time that like clockwork right? with your barrel being 20-30" wouldn't a 20fps difference in a round mess that timing up?
-why is the trend toward heavy bullets and high BC's in long range shooting, on ballistics calculator's it seems that speed makes a bigger difference in the trajectory of a round then heavy high BC rounds. why are bench rest shooters and long range tactical shooters/hunters leaning toward bigger bullets instead of higher speeds? wouldn't a 6mm with a relatively good BC shot at 4000 fps out perform say one of the 180gr .30's shot at 2800fps....just an example to convey the idea i didn't actually check this on a ballistic calculator. the question is if speed provides a bigger pay of in wind drift and drop then weight then why are the good shooters not shooting spectacularly over bored rifles? what specific advantages do big slow bullets have over small fast ones? www.lostriverballistic.com advertises a 160gr 7mm bullet that has a BC of .778 versus the .684 of the Berger 180gr bullet being 20gr lighter wouldn't u be able to drive this bullet faster not to mention the nearly .100 difference in ballistic coefficients so why the fuss for the Berger what do those 20gr do that that make it a better bullet? I'm assuming it must be a better bullet because men far wiser then me use it.

sorry for the spelling it's late here and i just got of work so it's not really well punctuated or spelled for that matter, but after all the reading i did tonight about rifles Ive just managed to confuse myself and stumble onto another bag of questions. sorry for any inconvenience

 

[CPorter]

I can't answer your questions on the extractor/ejectors assemblies or the bolt lugs. The types of question were supposedly examined in detail in Harold Vaughn's "Rifle Accuracy Facts".

Yes, velocity deviations cause problems. Most competition shooters reload to minimize extreme velocity spread. Tuning is also done to cause the bullets to exit at the peak of the sine wave were the dwell time is greatest and the effects of minor velocity changes are minimized. I'm sure some also tune to avoid the transverse pressure wave peaks at the muzzle.

Short range benchrest shooters around me seem to shoot light weight flat based bullets. They stabilize faster and suffer less effects from precession than longer heavier bullets. This supposedly affects them more than they gain in wind drift at that range.

Long range shooters like heavier bullets because they retain their velocity longer and suffer less wind drift. For example, at about 500 yards a certain 6mm 70gr bullet fired at 3800 fps has the same velocity as a 6mm 105 gr bullet fired at 2900 fps. As the range increases the 105 gr bullet has a higher velocity the the 70 gr bullet. At a certain range the bullets will go subsonic and generally the heavier higher BC bullet will do that at a longer range. The transition to subsonic causes a great deal of disturbance to the bullet path and therefore it is avoided if possible. At 500 yards that 70 gr bullet has about 2.12" of wind drift per every 1 mph of side wind and the 105 has only 1.5". Since the wind is seldom constant I have a better chance of hitting my target with the 105gr bullet.

 

[reimers84]

Long range shooters like heavier bullets because they retain their velocity longer and suffer less wind drift.

-by heavy do u mean having a higher ballistic coefficent or just heavier?

For example, at about 500 yards a certain 6mm 70gr bullet fired at 3800 fps has the same velocity as a 6mm 105 gr bullet fired at 2900 fps. As the range increases the 105 gr bullet has a higher velocity the the 70 gr bullet. At a certain range the bullets will go subsonic and generally the heavier higher BC bullet will do that at a longer range

-i understand what u are trying to say but im confused between weight and BC, isnt BC what callculates the bullets ability to carry energy downrange,inertia) or is it weight? for example the 160 grain lostriver 7mm bullet is lighter then the berger 180gr 7mm bullet BUT the 160gr bullet has a BC of .778 vs .684 for the heavier 180gr berger bullet. wont the bullet with the higher BC retain it's speed and wind restance longer even if it is lighter then the other bullet?

 

[CPorter]

In the same caliber and style of bullet a heavier bullet has a higher BC. In the same caliber a heavier bullet is also generally a longer bullet but not always. There are some tungsten core bullets out there somewhere that are shorter and heavier and there are alloy bullets,Lost River)that are longer and lighter. BC can be calculated:


BC = SD/i = w/id2

Where BC = ballistic coefficient
SD = sectional density
i = form factor
w = weight of bullet, lbs.
d = diameter of the bullet, in.

You can see by the formula that BC includes weight. The higher the weight the higher the BC. The formula also has a form factor. The more aerodynamic the bullet shape is the smaller the form factor and the higher the BC.

In the case of the Lost River vs Berger bullets you mentioned the improvements in the Lost River form factor,longer pointier nose) supposedly make more of an improvement to the BC than the increase in weight. And yes the Lost River bullet should carry more velocity downrange.